The objective is root causing the reliability issues in the HW/SW part of a thermal A6 printer unit being part of widely applied complex system. As the printers were already located in the field application, a board redesign was no option; only the software and firmware of the processor and programmable logic device of the printer electronics could be altered. Three major design flow shortages popped up immediately: The design was poorly documented and was not up-to-date, there were no DFT structures in place to run tests and diagnostics on the system and last but not least, there was a poor communication between the software and hardware team of company A (being the company that originally developed the system). As company A was not able to fix the issues, a third party consultant/design house (Q-Star Test) was selected to fix the bugs causing the printer to behave unreliable. The key in solving the issues was identifying and fixing the three shortcomings listed above. By doing so, the printer design was turned into a robust system that is easily tuneable. The new design also allowed to fix the print quality issues of which the old design also suffered but that could not be fixed due to the same three short comings identified above.